In a conventional control apparatus for an internal combustion engine installed in a vehicle, a throttle valve is operated when executing cranking on the internal combustion engine in order to start the internal combustion engine. As a result, negative pressure is generated rapidly on a downstream side of the throttle valve. Further, shock is suppressed during startup by securing torque continuity.
PTL 1 describes an example of a conventional control apparatus that performs this type of control. In PTL 1, a throttle valve is fully closed when cranking is executed so that negative pressure is generated rapidly on a downstream side of the throttle valve. The throttle valve is then opened to a preset throttle opening prior to a fuel injection timing. In so doing, an amount of air taken in during startup of the internal combustion engine is reduced, and as a result, an amount of torque generated during complete combustion in the internal combustion engine is suppressed. Further, torque continuity is secured by aligning a timing at which negative pressure in an intake passage reaches a peak with a timing at which the internal combustion engine reaches a complete combustion state, and as a result, shock generation in the internal combustion engine is prevented. Note that here, the complete combustion state denotes a state of complete combustion following the beginning of a startup operation in the internal combustion engine.